MULTIPLE_KERNEL_THREADS

    On I64 and Alpha systems, this keyword sets the MULTIPLE_KERNEL_
    THREADS bit in the dynamic segment (I64) or the image header
    (Alpha) of the image being built. This bit indicates to the image
    activator that the image can be run in a multiple kernel threads
    environment.

    If you specify this keyword for OpenVMS VAX links, it is ignored.

 UPCALLS

    This qualifier sets the UPCALLS bit in the OpenVMS dynamic
    segment (I64) or image header (Alpha and VAX) of the image being
    built. This bit indicates to the image activator that the process
    can receive upcalls from the OpenVMS scheduler.

    When the /THREADS_ENABLE qualifier is specified without either
    the MULTIPLE_KERNEL_THREADS or UPCALLS keyword, the linker sets
    both bits by default.